Cleaning metal strip



May 24, 1955 G. DURST 2,709,142

CLEANING METAL STRIP Filed Aug. 22. 1950 United States Patent O CLEANING METAL STRIP George Durst, Attleboro, Mass., assignor to Metals;& Controls Corporation, Attleboro, Mass., a corporation of Massachusetts Application August 22, 1950, Serial No. 180,829 4 Claims. (11. 134-9) This invention relates to cleaning metal strip, and more particularly to cleaning the opposed surfaces of metal strips which are to be solid phase bonded by rolling them together in a rolling mill.

1 have found that the opposed surfaces of metal strips which are to be solid phase bonded by rolling them together in a rolling mill, in such manner, for example, as disclosed in the two copending applications of myself and Helmich W. Boessenkool, one entitled Bonded Metals and Their Manufacture, Serial No. 86,857, filed April 11, 1949, now abandoned, the other entitled Solid Phase Bonding of Metals, Serial No. 204,346, filed January 4, 1951, now Patent No. 2,691,815, dated October 19, 1954, must be free from visible oxide film and other inorganic films and contaminants such as organic matter, moisture and adsorption films in order to obtain a satisfactory bond.

One way of cleaning a strip is to heat it to drive oil such contaminants as organic matter, moisture, and adsorption films and to abrade it to remove oxide and other inorganic films. This, however, engenders the problem as to how to heat and abrade the strip effectively to clean it without raising its body temperature to such a value that, immediately after cleaning, oxide film re-forms on the strip.

This invention involves a special method for cleaning metal strip by heating and abrading while avoiding any conditions favoring the re-forming of oxide film on the strip. in general, the method involves positively feeding a strip to be solid phase bonded over the periphery of a rotary scratch brush, holding the strip pressed against the brush to flatten the periphery of the brush, with the relationship of the speed of the strip, the speed of the brush and the penetration of the brush (this being herewith defined as the extent to which the brush is flattened where it engages the strip) such as to heat the surface of the strip to a temperature sufiiciently high to drive off such contaminants as organic matter, moisture and adsorption films, and to abrade off oxide and other inorganic films, the speed of the strip and the intensity of the surface heating being such that the heat is thereafter quickly dissipated away from the surface into the bulk of the strip so that the bulk and surface temperature of the strip after it passes the brush is below that at which visible oxide film rapidly forms. Other features will be in part apparent and in part pointed out hereinafter.

The invention accordingly comprises the steps and sequence of steps, and features of manipulation which will be exemplified in the methods hereinafter described, and the scope of the application of which will be indicated in the following claims.

In the accompanying drawing, in which one of various possible embodiments of the invention is illustrated:

Fig. 1 is a view in side elevation of an apparatus for carrying out the invention, with parts broken away and shown in section on line ll1 of Fig. 2; and

Fig. 2 is an end view of Fig. l as viewed from the right.

Referring to the drawing, an apparatus for carrying out the invention is shown to comprise a support consisting of a base 1 and side frames 3 extending vertically upward from the base. A circular wire-bristle brush 5 has a shaft 7 journalled in bearings in the side frames for rotation on a horizontal axis. The brush is adapted to be positively driven by a motor 9 mounted on the base 1, the shaft of the motor being coupled to the shaft 7 as by a belt and pulley drive generally designated 11. Above the brush is an upper back-up roll 13 and below the brush is a lower back-up roll 15. Rolls 13 and 15 have shafts 17 and 19, respectively, journalled in bearings 21 which are vertically adjustable in guideways 23 in the side frames. Any suitable and conventional means for adjusting the bearings may be used, for example, the screw-type adjustment generally indicated at 2d in Fig. 1. At 27 are shown corrugated guide rolls carried by arms 29 on the side frames for guiding a strip between the top of the brush and the upper back-up roll 13. Similar guide rolls could be provided for guiding a strip between the bottom of the brush and the lower back-up roll 15.

The above-described apparatus is used on the entrance side of a rolling mill, for cleaning the opposed surfaces of two metal strips A and B as they travel toward the rolls of the mill (as in the direction of the arrows shown in Fig. 1) wherein the strips are rolled to bond them together. The strips are positively pulled from roll supplies thereof by the mill and travel on opposite sides of the brush, which is wider than the widest strip to be accommodated. As shown, strip A travels between the top of the brush under the upper back-up roll 13 and strip B travels between the bottom of the brush and the lower back-up roll 15. The back-up rolls are adjusted to hold the strips pressed against the brush to flatten it to some extent. The brush is driven by the motor 9 as in the direction of the arrow shown in Fig. 1.

The brush 7 is a standard scratch brush having hard steel bristles. With a strip pressed against it, it is flattened to some extent so that it engages the strip over an abrading area of some length in the direction of length of the strip. The penetration is greatest at the transverse center line of the abrading area and diminishes toward the forward and rearward ends of the abrading area in the direction of length of the strip. As the strips A and B travel over the brush, their opposed surfaces are abraded, and become frictionally heated. Maximum heat is generated at the narrow transverse zones of the surfaces of the strips where the penetration of the brush is the greatest. For some metal strips, the surface metal might even melt at this zone. However, as soon as these surface Zones move forwardof the zones of greatest penetration of the brush, they start to cool. Cooling occurs mainly in three ways: (1) by How of cooling air created by the rotating brush; (2) by conduction of heat through the bristles of the brush; and (3) by flow of heat by conduction in the strips from their surfaces into their body or bulk.

The speed and energy input of the brush, the penetrations of the brush with respect to strips A and B, and the speed of travel of the strips are so selected that the lower surface of the upper strip A and the upper surface of the lower strip B are abraded clean of visible oxide film and any other inorganic film and heated at the point of maximum penetration to a temperature high enough to drive olf such contaminants as organic matter, moisture and adsorption films, without heating the body of the strips to such temperature, and also so that the brushed surfaces of the strips emerging from contact with the brush are cooled down below the temperatures at which visible oxide films would rapidly form on the strips. The cooling occurs mainly in the three ways above mentioned. It is highly important that the brush and strip speed and the penetrations be so selected that the body of each strip is not heated above the temperature at which oxide film forms, but only the strip surface that is so heated. The surface might even be melted, in the case of some metals, as long as the body of the strip is not highly heated. While there may be some tendency for oxide film to form at the zone of greatest penetration, any film forming in this zone is abraded oh by the bristles of the brush as the strip traveis forward from the zone of greatestpenetration to the forward end of the flattened peripheral area of the brush.

The above-described method and apparatus are suitable for cleaning many ditferent metals, for example steel, copper, silver, brass, stainless steel, copper-nickel alloys, bronze, aluminum. The speed of a strip, the speed of the brush and its energy input, and the penetration of the brush will of course vary, being dependent upon the characteristics and thickness of the metal being cleaned. In general, it may be said that best operation is attained by relating these factors by trial and error in such manner that the body temperature of a strip emerging from the brush is from 150' F. to 259 F. This means that the i localized surface temperature of the strip induced by the brushing, which is not readily measured, is much higher and sufficient to drive olf such volatile contaminants as organic matter, moisture, and adsorption films.

The determination of the proper strip speed, the brush speed, the penetration, and thus the energy input, is'neccssarily largely a matter of trial and error for each metal. The adjustment of penetration is critical, but must be determined largely by trial and error because, among other reasons, the periphery of the scratch brush is not a perfectly smooth cylinder, the bristles of the brush varying somewhat in length. The criterion for adjustment of'penetration is to insure that the body or bulk temperature of a strip emerging from contact with the brush is below that favoring the rapid formation of visible oxide film. The average penetration for most non-ferrous metals for a brush of 9 inches diameter is about inch. Representative strip speeds for this brush are in the range from two feet per minute to twenty-five feet per minute. The average and preferred speed is from six to ten feet per minute. Roughly, an energy input of from one-half to two horsepower is required per inch of metal brushed.

In view of the above, it will be seen that the several. objects of the invention are achieved and other advantageous results attained.

As many changes could be made in the above methods without departing from the scope of the invention, it is intended that allmatter contained in the above description or shown inthe accompanying drawing shall be interpreted as illustrative and not in a limiting sense.

I claim:

1. The method of cleaning a surface of a metal strip preliminary to solid phase bonding thereof with another strip. comprising positively feeding the strip over the periphery of a rotary scratch brush, positively rotating the brush to effect relative movement between the strip and the periphery of the brush, and causing the brush to penetrate the strip, the speed of the strip, the speed of the brush, and the penetration of the brush being such as to frictionally heat the surface of the strip to a temperature suificiently high to drive off such contaminants as Organic matter, moisture and adsorption films, while abrading oif oxide and other inorganic films, without heating the bulk of the strip to such temperature, and so that the temperature of the strip immediately after it passes the brush is below that at which visible oxide film rapidly forms on the newly brushed surface.

2. The method of cleaning a surface of a metal strip :3 preliminary to solid phase bonding thereof with another strip, comprising positively feeding the strip over the periphery of a rotary Wilfi-bKlStlG brush, positively rotating the brush to effect relative movement between the strip and the periphery" of the brush, and causing the bristles ofthe brush, to penetrate the strip, thespeecl of the strip, the speed; of the brush, and the penetration of the bristles being such as to frict'ionally heat the surface of the strip to a temperature sufiiciently high to drive oif such contaminants as organic matter, moisture and adsorption 3 films, while abrading off oxide and: other inorganic films,

without heating the bulk of the strip to such temperature, and so that the temperature of the strip immediately after it passes the brush is below that at which visiblc' oxide film can form rapidly.

31 The method of cleaning the opposed surfaces of two metal strips preliminary to solid phase bonding thereof, comprising positively feeding the strips over the periphery of a rotary scratch brush, one strip on one side and the other on the other side of the brush, positively rotating the brush to effect relative movement between the strips and theperiphery of the brush, and causing the brush to penetrate the strips, the speed of the strips, the speed of the brush, and the penetration of the brush being such as to frictionally heat the surfaces of the strips to a temperature sufiicicntly high to drive off such contaminants as organic matter, moisture and adsorption film's, while abradin'g off oxide and other inorganic films,

without heating the bulk of the strips to such temperature,

and so that the temperature of the strips immediately after they pass the brush is below that at which visible oxide film rapidly forms on the newly brushed surfaces.

4. The method of cleaning the opposedsurfaces of two metal strips preliminary to solid phase bonding thereof, comprising positively feeding the strips over the pe rip'h'ery ofa rotary wire-bristle brush, one strip on one side and the other strip on the other side of the brush, positively rotating the brush to effect relative movement between the strips and the periphery of the brush, and causing the bristles of the brush to penetrate the strips, the speed of the strips, the speed of the brush, and thepenetratjion of the bristles being such as to friction-ally heat the surfaces of the strips to a temperature sufficiently high to drive off such contaminants as organic matter, g moi's'ture and adsorption film-s, while abrading oft oxide and other inorganic films, without heating the bulk of the strips to such temperature, and so that the temperature of the strips immediately after they pass brush is below that at which visible oxides can rapidly form.

References Cited in the fileof this patent UNITED STATES PATENTS 

1. THE METHOD OF CLEANING A SURFACE OF A METAL STRIP PRELIMINARY TO SOLID PHASE BONDING THEREOF WITH ANOTHER STRIP, COMPRISING POSITIVELY FEEDING THE STRIP OVER THE PERIPHERY OF A ROTARY SCRATCH BRUSH, POSITIVELY ROTATING THE BRUSH OF EFFECT RELATIVE MOVEMENT BETWEEN THE STRIP AND THE PERIPHERY OF THE BRUSH, AND CAUSING THE BRUSH TO PENETRATE THE STRIP, THE SPEED OF THE STRIP, THE SPEED OF THE BRUSH, AND THE PENETRATION OF THE BRUSH BEING SUCH AS TO FRICTIONALLY HEAT THE SURFACE OF THE STRIP TO A TEMPERATURE SUFFICIENTLY HIGH TO DRIVE OFF SUCH CONTAMINANTS AS ORGANIC MATTER, MOISTURE AND ABSORBPTION FILMS, WITHOUT ABRADING OFF OXIDE AND OTHER INORGANIC FILMS, WITHOUT HEATING THE BULK OF THE STRIP TO SUCH TEMPERATURE, AND SO THAT THE TEMPERATURE OF THE STRIP IMMEDIATELY AFTER IT PASES THE BRUSH IS BELOW THAT AT WHICH VISIBLE OXIDE FILM RAPIDLY FORMS ON THE NEWLY BRUSHED SURFACE. 